A common problem for communication between a transmitter and one or more receivers in a radio communication network is called synchronization, in which the clocks at the transmitter and receiver(s) must be aligned so that the receiver(s) can properly interpret its reception of analog waves sent by the transmitter as discrete bits. This synchronization process is illustrated in FIGS. 1A and 1B. First, the transmitter prepares a pattern of short radio frequency (RF) pulses 105 and transmits them at time Ts 110. This pattern 105 is sometimes called the synchronization pattern or sequence. Second, the receiver receives the pulse pattern 105 after the pattern passes through the communications channel and noise, multi-path fading, and interference modify it. Third, the receiver is turned on at some time Tr 120, and the receiver then “looks” at the RF signal 115 it receives and performs some kind of pattern matching algorithm on the received RF signal in order to find a match for the expected transmitted pulse pattern 105 (i.e., the receiver has no knowledge of where pulse pattern 105 will occur in the received RF signal 115).
Once the receiver has found a pattern match 125, it can then synchronize its clock with that of the transmitter. This clock synchronization involves determining the time Ts 110 that the transmitter started transmitting pulse pattern 105 in a common reference time-frame. After the synchronization pattern is detected 130, and then acquired and matched at time Ta 135, both the receiver and transmitter will share a common reference time-frame, and can employ this time-frame for communication.
In ultra-wide band (UWB) radio communication, for example, the synchronization process can result in excessive energy consumption due to the length of time required to power the receiver to acquire the synchronization pattern, and the time required to power the circuitry executing the correlation algorithm. This excessive energy consumption results from two aspects of UWB radio communications: 1) the transmitted pulses are very short; and 2) the space between the pulses can be quite long relative to the pulse width. The short pulses cause the receiver to be powered up for an extended period of time before it acquires the transmitter's synchronization relative to the lengths of the pulses themselves. The long space between the pulses causes the correlation pattern matching to take longer due to a high quantity of noise within a received pattern. The combination of the short UWB pulses and the long intervals between pulses, therefore, leads to relatively large energy consumption for the receiving device when attempting to synchronize with the transmitting device.
Therefore, there exists a need for systems and methods that can reduce energy consumption requirements in a RF receiving device when synchronizing to a transmitting device.